Userland: Rename Core::Object to Core::EventReceiver

This is a more precise description of what this class actually does.

Userland/Applications/Piano/AudioPlayerLoop.h

@@ -13,7 +13,7 @@
 #include <LibAudio/Sample.h>
 #include <LibAudio/WavWriter.h>
 #include <LibCore/Event.h>
-#include <LibCore/Object.h>
+#include <LibCore/EventReceiver.h>
 #include <LibDSP/Music.h>
 #include <LibThreading/MutexProtected.h>
 #include <LibThreading/Thread.h>
@@ -22,7 +22,7 @@ class TrackManager;
 
 // Wrapper class accepting custom events to advance the track playing and forward audio data to the system.
 // This does not run on a separate thread, preventing IPC multithreading madness.
-class AudioPlayerLoop final : public Core::Object {
+class AudioPlayerLoop final : public Core::EventReceiver {
     C_OBJECT(AudioPlayerLoop)
 public:
     virtual ~AudioPlayerLoop() override;

Userland/Applications/Piano/ProcessorParameterWidget/ParameterWidget.h

@@ -7,7 +7,7 @@
 #pragma once
 
 #include <AK/NonnullRefPtr.h>
-#include <LibCore/Object.h>
+#include <LibCore/EventReceiver.h>
 #include <LibDSP/ProcessorParameter.h>
 #include <LibGUI/Label.h>
 #include <LibGUI/Widget.h>

Userland/Applications/Piano/ProcessorParameterWidget/Toggle.h

@@ -6,7 +6,7 @@
 
 #pragma once
 
-#include <LibCore/Object.h>
+#include <LibCore/EventReceiver.h>
 #include <LibDSP/ProcessorParameter.h>
 #include <LibGUI/CheckBox.h>
 #include <LibGUI/Widget.h>